1. Field of the Invention
This invention relates to door latching apparatus and, in particular, to tamper-proof lock apparatus for application to the exterior portion of a door.
2. Description of the Prior Art
Frequently, the integrity of door locking methods and apparatus is compromised by the necessity of providing exterior access to the lock. This is common to most lock uses, although various schemes have been employed to minimize the exposure of vulnerable lock portions to a would-be tamperer. Wooden doors having significant depth are commonly employed in residential dwellings. This allows the recessing of the door lock well into the door. An intruder is left only with the relatively flush face of the lock in any attempt to disable its mechanism. These recessed locks are fairly effective against all but the most sophisticated and generally must be "picked" to be overcome. Additionally, residential applications are aided by the fact that, in a well-populated area, it would be unseemly and, therefore unlikely, for an intruder to take the extensive measures required to separate such a well-anchored lock from the door.
Non-residential uses such as warehouses and businesses face tampering problems much more severe than residences. These applications are frequently located in areas that are relatively unpopulated during the night. Security guard services, to be effective, involve considerable expense in view of large areas of vulnerability which must be canvassed in regard to any large warehouse. Often it is expensive and impractical to provide a door of sufficient depth to anchor and conceal a lock. (This problem is also encountered in residence garages.) The advent of "mini-warehouses", a boon to the storage of the entire spectrum of manufactured goods and the like, comprise, generally, pre-fabricated walls and metallic roll-down doors of sheet metal of minimal thickness. The metal door is often corrugated. These warehouses commonly employ an exteriorly mounted latching mechanism which includes mating parts which are secured in latching position by the use of a standard padlock.
The padlocks employed in present-day latching mechanisms are often vulnerable to tampering on two counts. A padlock commonly comprises a relatively sturdy body which is engageable to a U-shaped shackle portion. The shackle is generally tubular throughout its U-shape. A standard hacksaw or bolt cutter is generally capable of severing the shackle, allowing the latching mechanism to be disengaged. An additional vulnerability of such latching mechanism is that the body of the lock may be dislodged from its shackles by the sharp blow of a hammer or other blunt instrument. Thus, the exteriorly mounted latching mechanisms of the prior art, frequently employing one or more standard padlocks, present apparatus of unacceptable vulnerability for a variety of applications.
Thus, it may be seen that a tamper-free exterior lock apparatus is desired for the latched securing of a door of the type commonly employed in warehouses, garages, etc. which is invulnerable to the type of tampering generally encountered by padlocked latching mechanisms.